Retractable lens system and method of retracting a retractable lens system

ABSTRACT

A retractable lens system includes a plurality of optical elements. All of the plurality of optical elements are positioned on a common optical axis when the retractable lens is in use. A removable element of the plurality of optical elements is moved to a removed position outside of the common optical axis, and the removable element and at least one element of the remaining elements of the plurality of optical elements are moved rearward, respectively, when the retractable lens system is in a retracted position.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a retractable lens system whichcan extend from and retract into a body of an optical instrument such asa camera using sensitive film or a digital camera using a CCD or CMOSimage sensor. The present invention also relates to a method ofretracting such a retractable lens system.

[0003] 2. Description of the Related Art

[0004] The demand for miniaturization in compact cameras is everincreasing. Specifically, in cameras having a retractable photographinglens, there has been a strong demand for further reduction of the lengthof the retractable photographing lens when fully retracted.

SUMMARY OF THE INVENTION

[0005] The present invention provides a retractable lens having astructure making it possible to further reduce the length of theretractable lens when it is fully retracted. The present inventionfurther provides a method of retracting a retractable lens which makesit possible to further reduce the length of the retractable lens when itis fully retracted.

[0006] According to an aspect of the present invention, a retractablelens having an optical system including a plurality of optical elementsis provided. All of the plurality of optical elements are positioned ona common optical axis to constitute a photographing optical system whenthe retractable lens system is in a ready-to-photograph position. Atleast one removable element of the plurality of optical elements ismoved to a removed position outside of the common optical axis, and theremovable element and at least one element of the remaining elements ofthe plurality of optical elements are moved rearward, respectively, whenthe retractable lens system is in a retracted position.

[0007] It is desirable for the removable element to be positionedoutside of at least one element of the remaining elements of theplurality of optical elements with respect to the common optical axiswhen the retractable lens system is in a retracted position.

[0008] The removable element can move rearward parallel to the commonoptical axis after being moved to the removed position when theretractable lens system moves to the retracted position.

[0009] An optical axis of the removable element of the optical elementscan be parallel to the common optical axis when the retractable lens isin the retracted position.

[0010] The optical elements can include a plurality of the removableelements.

[0011] Each removable element of the plurality of removable elements canbe moved in different directions from the common optical axis to eachrespective the removed position.

[0012] It is desirable for a rotational axis of a rotational member formoving at least one of the plurality of optical elements along thecommon optical axis to be eccentric to the common optical axis of thephotographing optical system.

[0013] It is desirable for the removable element of the optical elementsto be positioned within the periphery of the rotational member when theretractable lens is in the retracted position.

[0014] The rotational member can be a cam ring.

[0015] The retractable lens can be incorporated in a camera.

[0016] It is desirable for the retractable lens moves to the retractedposition when a main switch of the camera is turned OFF.

[0017] According to another aspect of the present invention, a method ofretracting a retractable lens system having a plurality of opticalelements is provided, wherein all of the plurality of optical elementsare positioned on a common optical axis to constitute a photographingoptical system when the retractable lens system is in aready-to-photograph position. The method includes moving at least oneelement of the plurality of optical elements in a radial direction to aremoved position outside of the common optical axis; retracting theremovable element of the optical elements rearward after being moved tothe removed position; and retracting at least one element of theremaining elements of the plurality of optical elements along the commonoptical axis.

[0018] The removable element can be positioned outside of at least oneelement of the remaining elements of the plurality of optical elementswith respect to the common optical axis, when the retractable lenssystem is in a retracted position.

[0019] The removable element can move rearward parallel to the commonoptical axis after being moved to the removed position.

[0020] An optical axis of the removable element of the optical elementscan be parallel to the common optical axis when the retractable lenssystem is in the retracted position.

[0021] According to another embodiment, a retractable zoom lens systemis provided, wherein at least a portion of the lens groups are movedcontinuously along an optical axis to vary a focal length; wherein atleast one radially movable lens group of the plurality of lens groups isradially moved from among the plurality of lens groups so that theradially movable lens group and at least one lens group of the remaininglens groups of the plurality of lens groups are positioned so as tooverlap in the same positional range in the optical axis direction whenthe retractable zoom lens is in the retracted position.

[0022] It is desirable for the radially movable lens group to be thesmallest in diameter among the plurality of lens groups.

[0023] The retractable zoom lens system can further include anadjustable diaphragm having an aperture the diameter of which beingvariable. The adjustable diaphragm can positioned between two adjacentlens groups of the plurality of lens groups. The radially movable lensgroup is at a position behind the adjustable diaphragm when the zoomlens system is in a ready-to-photograph position.

[0024] The adjustable diaphragm can serve as a diaphragm shutter.

[0025] The retractable zoom lens system can further include anadjustable diaphragm having an aperture the diameter of which isvariable. The adjustable diaphragm is positioned between two adjacentlens groups of the plurality of lens groups. The radially movable lensgroup is positioned closest to the adjustable diaphragm among theplurality of lens groups when the zoom lens system is in aready-to-photograph position.

[0026] The adjustable diaphragm can serve as a diaphragm shutter.

[0027] It is desirable for the radially movable lens group to be at aposition behind a frontmost lens of the plurality of lens groups.

[0028] The present disclosure relates to subject matter contained inJapanese Patent Application No. 2002-44306 (filed on Feb. 21, 2002)which is expressly incorporated herein by reference in its entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will be described below in detail withreference to the accompanying drawings in which:

[0030]FIG. 1 is a longitudinal cross-sectional view of an embodiment ofa retractable zoom lens of a digital camera in a ready-to-photographstate, according to the present invention;

[0031]FIG. 2 is a longitudinal cross-sectional view of the retractablezoom lens shown in FIG. 1 in a fully retracted state when the camera isnot in use;

[0032]FIG. 3A is a cross sectional view of fundamental elements (whichincludes lens groups, a diaphragm shutter, a low-pass filter and a CCD)of the retractable zoom lens shown in FIG. 1;

[0033]FIG. 3B is a cross sectional view of fundamental elements (shownin FIG. 3A) of the retractable zoom lens shown in FIG. 2;

[0034]FIG. 4 is an exploded perspective view of fundamental elements ofthe retractable zoom lens shown in FIGS. 1 and 2;

[0035]FIG. 5A is a front elevational view of the fundamental elementsshown in FIG. 4, with a linear guide ring removed for clarity, in aready-to-photograph state;

[0036]FIG. 5B is a view similar to that of FIG. 5A and illustrates thefundamental elements shown in FIG. 4, with the linear guide ring removedfor clarity, in a fully retracted state;

[0037]FIG. 6A is a perspective view of the elements shown in FIG. 5A,wherein a stationary ring member is partially cutaway for clarity;

[0038]FIG. 6B is a perspective view of the elements shown in FIG. 5B,wherein a second lens group support frame is partially cutaway forclarity;

[0039]FIG. 7A is a front elevational view of the fundamental elementsshown in FIG. 4, in a ready-to-photograph state, with the linear guidering and the second lens group support frame being removed for clarity;

[0040]FIG. 7B is a view similar to that of FIG. 7A and illustrates thefundamental elements shown in FIG. 4, in a fully retracted state, withthe linear guide ring and the second lens group support frame beingremoved for clarity;

[0041]FIG. 8A is a perspective view of the elements shown in FIG. 7A;

[0042]FIG. 8B is a perspective view of the elements shown in FIG. 7B;

[0043]FIG. 9 is an enlarged perspective view of the elements shown inFIGS. 7B and 8B;

[0044]FIG. 10A is a perspective view of fundamental elements of theretractable zoom lens shown in FIG. 1, showing a support structuresupporting a retractable lens group frame on the second lens groupsupport frame, as viewed from behind in the optical axis direction ofthe retractable zoom lens;

[0045]FIG. 10B is a view similar to that of FIG. 10A, showing the samesupport structure in a different state;

[0046]FIG. 11 is a longitudinal cross-sectional view of a secondembodiment of a retractable zoom lens in a fully retracted state,according to the present invention;

[0047]FIG. 12 is a longitudinal cross-sectional view of a thirdembodiment of a retractable zoom lens in a fully retracted state,according to the present invention;

[0048]FIG. 13 is a longitudinal cross-sectional view of a fourthembodiment of a retractable zoom lens in a fully retracted state,according to the present invention;

[0049]FIG. 14 is a front elevational view of a camera showing an exampleof optical elements removed from the optical axis of the retractablezoom lens; and

[0050]FIG. 15 is a front elevational view of a camera showing anotherexample of optical elements removed from the optical axis of theretractable zoom lens.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0051] The overall structure of a first embodiment of a retractable zoomlens according to the present invention will be hereinafter discussedwith reference to FIGS. 1 through 3. The retractable zoom lens 10 isincorporated in a digital camera, and is provided with a photographingoptical system having a first lens group L1, a diaphragm shutter S, asecond lens group (radially movable portion/removable optical element)L2, a third lens group L3, a low-pass filter (optical filter) F, and aCCD image sensor (image pick-up device) C. “Z1” shown in FIG. 1designates the optical axis of the photographing optical system. Thefirst lens group L1 and the second lens group L2 are driven along theoptical axis Z1 in a predetermined moving manner to perform a zoomingoperation, while the third lens group L3 is driven along the opticalaxis Z1 to perform a focusing operation. Note that the zooming operationcan be performed by moving at least two lens groups in the optical axisdirection, respectively, such as in the present embodiment, or by movingat least one lens group and the image surface (for example the CCD imagesensor) in the optical axis direction, respectively.

[0052] As clearly seen in FIGS. 1 and 2, the second lens group L2 is thesmallest in diameter among all the three lens groups L1, L2 and L3.

[0053] In the retractable zoom lens 10 having the above describedphotographing optical system, all the optical elements of thephotographing optical system are positioned on the common optical axisZ1 in a ready-to-photograph state as shown in FIGS. 1 and 3A; whereasthe second lens group L2 removed from a position on the optical axis Z1in a direction perpendicular to the optical axis Z1 to be positioned onan eccentric optical axis (removable-element optical axis) Z1′ (seeFIGS. 2 and 3B) in a fully retracted state (retracted position) as shownin FIGS. 2 and 3B. When the second lens group L2 is moved to the removedposition, the second lens group L2 does not overlap the other opticalelements of the photographing optical system (i.e., the first lens groupL1, shutter S, the third lens group L3, the low-pass filter F and theCCD image sensor C) in the optical axis direction. At the same time, inthe fully retracted state, the second lens group L2 (i.e., an opticalelement having been removed from the optical axis Z1) is retracted alongthe eccentric optical axis Z1′ while also at least one of the remainingoptical elements of the photographing optical system, which are notremoved from the optical axis Z1, are retracted along (parallel to) theoptical axis Z1. The manner of such movements of the optical elements ofthe photographing optical system makes a further reduction of the lengthof the retractable zoom lens 10 possible when the retractable zoom lens10 is fully retracted.

[0054] When the retractable zoom lens 10 is changed from theready-to-photograph state shown in FIGS. 1 and 3A to the fully retractedstate shown in FIGS. 2 and 3B, firstly the second lens group L2 isradially retracted from a position on the optical axis Z1 to be placedon the eccentric optical axis Z1′, which is eccentric with respect tothe optical axis Z1, on which the remaining optical elements of thephotographing optical system lie. Subsequently, the second lens group L2is retracted along the eccentric optical axis Z1′ and at the same timethe first lens group L1, the diaphragm shutter S and the third lensgroup L3, among the aforementioned remaining optical elements of thephotographing optical system, are retracted along the optical axis Z1.In the fully retracted state (fully accommodated state) shown in FIGS. 2and 3B, the removed second lens group L2 which lies on the eccentricoptical axis Z1′ and other optical elements of the photographing opticalsystem which lie on the optical axis Z1 (i.e., the third lens group L3,the low-pass filter F and the CCD image sensor C in this particularembodiment) are positioned so as to overlap in the same positional rangein the optical axis direction of the optical axes Z1 and Z1′. In otherwords, the second lens group L2 is positioned outside of the third lensgroup L3, the low-pass filter F, and the CCD image sensor C with respectto the optical axis Z1 (in the direction perpendicular to the opticalaxis Z1), in the fully retracted state.

[0055] The structure of the retractable zoom lens 10 which makes itpossible to achieve the above described manner of retraction of theoptical elements of the photographing optical system will be discussedin detail with reference mainly to FIGS. 1 and 2. The retractable zoomlens 10 is provided with a CCD frame 11, a stationary barrel 12 and afront exterior frame 13, which are all stationary elements. The low-passfilter F and the CCD image sensor C are fixed to the CCD frame 11. Thefront exterior frame 13 is provided with an opening 13 a through whichouter and inner linear barrels 16 and 17 extend and retract theretractable zoom lens 10.

[0056] A rotating ring 14 is fitted on the stationary barrel 12 to berotatable about a rotational axis Z2 and to be immovable along therotational axis Z2. The stationary barrel 12 is provided on an outerperipheral surface thereof with a set of radial projections 12 a, andthe rotating ring 14 is provided on an inner peripheral surface thereofwith a corresponding set of circumferential grooves 14 a in which theset of radial projections 12 a of the stationary barrel 12 arerespectively engaged to be slidable in the set of circumferentialgrooves 14 a therealong. Due to the engagement of the radial projections12 a with the circumferential grooves 14 a, the rotating ring 14 issupported by the stationary barrel 12 to be rotatable thereon about therotational axis Z2 while being prevented from moving along therotational axis Z2.

[0057] The rotating ring 14 is provided on an outer peripheral surfacethereof with a circumferential gear 14 b which is in mesh with a pinion15. The pinion 15 is driven to rotate by a motor M (see FIG. 1).Rotating the pinion 15 forward and reverse by the motor M causes therotating ring 14 to rotate forward and reverse about the rotational axisZ2. The rotational axis Z2 is eccentric to the optical axis Z1 of thephotographing optical system. The rotating ring 14 is provided on aninner peripheral surface thereof with a set of rotation transfer grooves14 c. Annular members (16, 17, 18, 19 and 20) which will be hereinafterdiscussed are arranged coaxially about the rotational axis Z2.

[0058] The retractable zoom lens 10 is provided therein with the outerand inner linear barrels 16 and 17, a cam ring (rotational member) 18, alinear guide ring 19 and a second lens group support frame 20, in thatorder in a radial direction from the outside of the retractable zoomlens 10 to the rotational axis Z2. The stationary barrel 12 is providedon an inner peripheral surface thereof with a set of linear guidegrooves 12 b, and the linear guide ring 19 is provided on an outerperipheral surface thereof with a corresponding set of linear guideprojections 19 a which are respectively engaged in the set of linearguide grooves 12 b. The linear guide ring 19 moves only along theoptical axis Z1. The linear guide ring 19 is provided on an outerperipheral surface thereof with a circumferential projection 19 b, whilethe cam ring 18 is provided on an inner peripheral surface thereof witha circumferential groove 18 a in which the circumferential projection 19b is engaged. The engagement of the circumferential projection 19 b inthe circumferential groove 18 a allows the cam ring 18 to rotate aboutthe rotational axis Z2 with respect to the linear guide ring 19 whilepreventing the cam ring 18 and the linear guide ring 19 from movingalong the optical axis Z1 relative to each other. The cam ring 18 movesalong the optical axis Z1 together with the linear guide ring 19whenever moving along the optical axis Z1, and is rotatable about therotational axis Z2 relative to the linear guide ring 19.

[0059] The stationary barrel 12 is provided with a set of cam throughslots 12 c which radially extend through the wall of the stationarybarrel 12. The cam ring 18 is provided with a corresponding set offollower pins 18 b which extend radially outwards to extend through thestationary barrel 12 through the set of cam through slots 12 c to beengaged in the set of rotation transfer grooves 14 c, respectively. Thecam profile of the cam through slots 12 c is determined so that the camring 18 firstly moves to the most extended position thereof shown inFIG. 1 and thereafter only rotates about the rotational axis Z2 viaengagement of the cam through slots 12 c with the rotation transfergrooves 14 c when the rotating ring 14 is driven to rotate in a forwardrotational direction to extend the outer and inner linear barrels 16 and17 from the opening 13 a in a fully retracted state shown in FIG. 2.

[0060] The cam ring 18 is provided on an inner peripheral surfacethereof with a set of cam grooves 18 c in which a set of followerprojections 20 a which are formed on an outer peripheral surface of thesecond lens group support frame 20 are respectively engaged. The camring 18 is provided on an outer peripheral surface thereof with a set ofcam grooves 18 d in which a set of follower pins 17 a which are formedon an inner peripheral surface of the inner linear barrel 17 arerespectively engaged. As shown in FIG. 4, the second lens group supportframe 20 is provided on an outer peripheral surface thereof with a setof linear guide grooves 20 b, and the linear guide ring 19 is providedon front thereof with a set of linear guide bars 19 c which arerespectively engaged in the set of linear guide grooves 20 b to beslidable thereon in the direction of the optical axis Z1, i.e., in theoptical axis direction of the photographing optical system of theretractable zoom lens 10. The second lens group support frame 20 isguided in the direction of the optical axis Z1 by engagement of thelinear guide bars 19 c with the linear guide grooves 20 b. Therefore,forward and reverse rotations of the cam ring 18 cause the second lensgroup support frame 20 to move forward and rearward along the rotationalaxis Z2 in accordance with the contours of the set of cam grooves 18 c.

[0061] The outer and inner linear guide barrels 16 and 18 are coupled toeach other so as to move together while being allowed to rotate relativeto each other about the rotational axis Z2. Namely, a set of radialprojections 18 f formed on an outer peripheral surface of the cam ring18 are slidably engaged in a corresponding set of circumferentialgrooves 16 a formed on an inner peripheral surface of the outer linearguide barrel 16.

[0062] The outer linear guide barrel 16 is supported by the stationarybarrel 12 to be movable only in the direction of the rotational axis Z2with respect to the stationary barrel 12, while the inner linear guidebarrel 17 is supported by the outer linear guide barrel 16 to be movableonly in the direction of the rotational axis Z2 with respect to theouter linear guide barrel 16. Namely, a set of linear guide projections16 b which project from an outer peripheral surface of the outer linearguide barrel 16 are engaged in a corresponding set of linear guidegrooves 12 d which are formed on an inner peripheral surface of thestationary barrel 12 to extend parallel to the rotational axis Z2, and aset of linear guide projections 17 b which project from an outerperipheral surface of the inner linear guide barrel 17 are engaged in acorresponding set of linear guide grooves 16 c which are formed on aninner peripheral surface of the outer linear guide barrel 16 to extendparallel to the rotational axis Z2. Therefore, forward and reverserotations of the cam ring 18 cause the inner linear guide barrel 17 tomove forward and rearward along the rotational axis Z2 rotational axisZ2 in accordance with the contours of the set of cam grooves 18 d.

[0063] The inner linear guide barrel 17 serves as a first lens groupsupport frame for supporting the first lens group L1. The retractablephotographing lens 10 is provided therein with a rotatable lens frame 21which serves as a second lens group support frame for supporting thesecond lens group L2. The retractable photographing lens 10 is providedtherein in front of the CCD frame 11 with a third lens frame 22 forsupporting the third lens group L3. As shown in FIG. 4, the third lensframe 22 is provided with two radial arms 22 a which extend radiallyoutwards in substantially opposite directions. The third lens frame 22is provided on an end of each radial arm 22 a with a linear guide hole22 b. One of the two radial arms 22 a is provided in the vicinity of theassociated linear guide hole 22 b with a cylindrical portion 22 c whichextends forward in parallel to the optical axis Z1 and in which a femalescrew hole is formed. A feed screw shaft (not shown) is screwed into thefemale screw hole of the cylindrical portion 22 c. Due to thisstructure, the third lens frame 22 is driven to move forward andrearward along the optical axis Z1 by a mechanism including the linearguide holes 22 b of the two radial arms 22 a, the cylindrical portion 22c and the aforementioned feed screw shaft when the feed screw shaftrotates forward and reverse. The feed screw shaft is rotated by an angleof rotation (the number of revolutions) determined by an object distance(lens-to-subject distance).

[0064] As described above, the second lens group L2 is removed from aposition on the optical axis Z1 when the retractable zoom lens 10 isfully-retracted-barrel state. The mechanism for pulling the second lensgroup L2 out of a position on the optical axis Z1 will be hereinafterdiscussed in detail with reference mainly to FIGS. 4 through 10.

[0065] The rotatable lens frame 21 is provided with a cylindrical lensholder portion 21 a, a swing arm 21 b and a cylindrical swing portion 21c. The second lens group L2 is fixed to the cylindrical lens holderportion 21 a to be supported thereby. The swing arm 21 b extendsradially from the cylindrical lens holder portion 21 a. The cylindricalswing portion 21 c extends rearward from a free end of the swing arm 21b. The cylindrical swing portion 21 c is provided along an axis thereofwith a through hole to be fitted on an eccentric pivot 20 c of thesecond lens group support frame 20 so that the rotatable lens frame 21is freely rotatable about the eccentric pivot 20 c. The eccentric pivot20 c extends parallel to the optical axis Z1 from the second lens groupsupport frame 20 from a position thereon eccentric to the optical axisZ1. The second lens group L2, which is fixed 15 to the cylindrical lensholder portion 21 a, is movable between a photographing position on theoptical axis Z1 (see FIGS. 5A, 6A, 7A, 8A and 10A) and a removedposition (eccentric position), i.e., a position eccentric away from theoptical axis Z1 (see FIGS. 5B, 6B, 7B, 8B and 10B), by a swing movementof the second lens group support frame 20 about the eccentric pivot 20c. The rotatable lens frame 21 is always biased to rotate in arotational direction (counterclockwise direction as viewed in each ofFIGS. 5A, 5B, 6A and 6B) that positions the second lens group L2, whichis held by the cylindrical lens holder portion 21 a, on the optical axisZ1 by a torsion spring 23 (see FIG. 1) positioned between the eccentricpivot 20 c and the cylindrical swing portion 21 c. The rotatable lensframe 21 is provided at a free end (swinging end) thereof (at theopposite end with respect to the cylindrical swinging portion 21 c) withan engaging protrusion 21 d which extends from the cylindrical lensholder portion 21 a in a direction away from the pivoted end of therotatable lens frame 21. The second lens group support frame 20 isprovided on an inner peripheral surface thereof with a stop protrusion20 d (see FIGS. 6A, 10A and 10B) against which the engaging protrusion21 d abuts when the second lens group support frame 20 fully rotatescounterclockwise to a position as viewed in FIGS. 5A and 6A. The secondlens group support frame 20 is provided with a cutaway portion 20 f intowhich the cylindrical swing portion 21 c partly enters when the secondlens group L2 moves to the removed position (eccentric position) on theoptical axis Z1′, as shown in FIGS. 5B and 6B.

[0066] The cylindrical swing portion 21 c is provided on an outerperipheral surface thereof with a position-control projection 21 f,while the CCD frame 11 is provided on a front surface thereof with aposition-control cam bar 11 a which extends forward. Theposition-control cam bar 11 a is engaged with the position-controlprojection 21 f to control the position of the rotatable lens frame 21.As can be clearly seen in FIG. 9, the position-control cam bar 11 aprojects forward from a base 11 b of the CCD frame 11 to extend parallelto the rotational axis Z2. The position-control cam bar 11 a is providedalong an inner side edge thereof with an removed-position holdingsurface 11 a 1 which extends parallel to the rotational axis Z2, and isfurther provided at a front end of the position-control cam bar 11 awith a cam surface 11 a 2 which is inclined rearwards, toward the base11 b, from an outer side edge 11 a 3 to the removed-position holdingsurface 11 a 1. In a state where the position-control projection 21 f ofthe rotatable lens frame 21 is engaged with the removed-position holdingsurface 11 a 1, the second lens group L2 is positioned in the removedposition, which is eccentric away from the optical axis Z1. In thisstate, if the rotatable lens frame 21 moves forward along the rotationalaxis Z2 up to a point where the position-control projection 21 f isengaged with the cam surface 11 a 2, the rotatable lens frame 21 rotatesabout the eccentric pivot 20 c by the spring force of the torsion spring23 to move the second lens group L2, which is held by the cylindricallens holder portion 21 a, onto the optical axis Z1. The position of thecylindrical lens holder portion 21 a at this time, when the second lensgroup L2 is moved onto the optical axis Z1 by the spring force of thetorsion spring 23, is defined by the engagement of the stop protrusion20 d with the engaging protrusion 21 d. At this time, the optical axisof the second lens group L2 is coincident with the optical axis Z1. Whenthe second lens group L2 is in the photographing position on the opticalaxis Z1 in a ready-to-photograph state, the position-control projection21 f is disengaged from the cam surface 11 a 2, and is positioned infront of the cam surface 11 a 2.

[0067] Conversely, in a state where the second lens group L2 is in thephotographing position on the optical axis Z1 in a ready-to-photographstate, if the rotatable lens frame 21 moves rearward along therotational axis Z2, firstly the position-control projection 21 f isengaged with the cam surface 11 a 2 and subsequently the rotatable lensframe 21 rotates about the eccentric pivot 20 c so that the second lensgroup L2 moves to a position (removed position) on the eccentric opticalaxis Z1′ from a position on the optical axis Z1 by engagement of theposition-control projection 21 f with the cam surface 11 a 2. In thisstate where the second lens group L2 is in the removed position on theeccentric optical axis Z1′, the cylindrical swing portion 21 c is partlypositioned in the cutaway portion 20 f. At this time, the eccentricoptical axis Z1′ is positioned within the second lens group supportframe 20 and within the inner periphery of the cam ring 18. In otherwords, although the cylindrical swing portion 21 c is partly positionedin the cutaway portion 20 f, with the eccentric optical axis Z1′positioned within the second lens group support frame 20, the eccentricoptical axis Z1′ is positioned such that the cylindrical swing portion21 c does not interfere with a rotational member such as the cam ring18.

[0068] Operations of the retractable zoom lens 10 having the abovedescribed structure will be hereinafter discussed. When the retractablezoom lens 10 is in the fully retracted position as shown in FIGS. 2 and3B, the outer linear barrel 16, the inner linear barrels 17, the camring 18, and the linear guide ring 19 are all fully accommodated in theopening 13 a of the front exterior frame 13. In this state, immediatelyafter a main switch MS (see FIG. 1) of the digital camera is turned ON,the rotating ring 14 is driven to rotate in a predetermined rotationaldirection by forward rotation of the pinion 15 to extend the outer andinner linear barrels 16 and 17 forward from the opening 13 a by apredetermined angle of rotation so that the retractable zoom lens 10changes from the fully retracted state to a ready-to-photograph state atthe wide-angle extremity. The rotation of the rotating ring 14 istransferred to the cam ring 18, so that the cam ring 18 advances to themost extended position thereof by engagement of the set of follower pins18 b with the set of cam through slots 12 c. In the process of thismovement of the cam ring 18 to the frontmost position thereof, the outerlinear barrel 16, the inner linear barrels 17, the cam ring 18 and thelinear guide ring 19 extend forward from the opening 13 a. Subsequently,the linear guide ring 19 and the outer linear barrel 16 linearly moveforward together with the cam ring 18 while each of the inner linearbarrel 17 and the second lens group support frame 20 advances toward aready-to-photograph position thereof at the wide-angle extremity.Thereafter, when the second lens group support frame 20 advances to theready-to-photograph position thereof at the wide-angle extremity, theposition-control projection 21 f advances while sliding on theremoved-position holding surface 11 a 1 to move from theremoved-position holding surface 11 a 1 to the cam surface 11 a 2.Immediately after the position-control projection 21 f moves to the camsurface 11 a 2 from the removed-position holding surface 11 a 1, therotatable lens frame 21 rotates about the eccentric pivot 20 c by thespring force of the torsion spring 23 in a direction to move the secondlens group L2 until the stop protrusion 20 d abuts against the engagingprotrusion 21 d, whereat the optical axis of the second lens group L2coincides with the optical axis Z1. This state where the stop protrusion20 d is engaged with the engaging protrusion 21 d is aready-to-photograph state at the wide-angle extremity as shown in FIGS.1 and 3A.

[0069] In this ready-to-photograph state at the wide-angle extremity, ifa zoom switch ZS (see FIG. 1) is manually operated to drive the pinion15, the cam ring 18 rotates about the rotational axis Z2 at a fixedposition without moving along the rotational axis Z2 (optical axis Z1).This rotation of the cam ring 18 causes the second lens group supportframe 20 and the inner linear barrel 17 to move along the rotationalaxis Z2 (optical axis Z1) in a predetermined moving manner in accordancewith the contours of the set of cam grooves 18 c and the contours of theset of cam grooves 18 d, respectively. Since the second lens groupsupport frame 20 carries the rotatable lens frame 21 while the firstlens group L1 is supported by the inner linear barrel 17, a zoomingoperation is performed by movements of the first and second lens groupsL1 and L2 along the optical axis Z1. A focusing operation is performedby driving the third lens group L3 along the optical axis Z1 inaccordance with an object distance.

[0070] Immediately after the main switch MS of the digital camera isturned OFF, the pinion 15 is driven reverse to move the cam ring 18rearward beyond the wide-angle extremity position thereof. In theprocess of this rearward movement of the cam ring 18, the second lensgroup support frame 20 and the inner linear barrel 17 move rearwardalong the rotational axis Z2 due to engagement of the set of cam grooves18 c with the set of follower projections 20 a and engagement of the setof cam grooves 18 d with the set of follower pins 17 a. The rearwardmovement of the second lens group support frame 20 firstly causes theposition-control projection 21 f of the rotatable lens frame 21 to comeinto contact with the cam surface 11 a 2 of the position-control cam bar11 a, and subsequently causes the rotatable lens frame 21 to rotateabout the eccentric pivot 20 c by engagement of the position-controlprojection 21 f with the cam surface 11 a 2 so that the second lensgroup L2 withdraws from the optical axis Z1. Subsequently, theposition-control projection 21 f moves onto the removed-position holdingsurface 11 a 1 from the cam surface 11 a 2 to hold the second lens groupL2 in the removed position thereof. Subsequently, the cam ring 18further moves rearward after the second lens group L2 has removed to bepositioned on the eccentric optical axis Z1′ while the inner linearbarrel 17, which supports the first lens group L1, moves rearward due tothe engagement of the set of cam grooves 18 c with the set of followerprojections 20 a. At the same time, the second lens group support frame20 moves rearward due to engagement of the set of cam grooves 18 d withthe set of follower pins 17 a, while the position-control projection 21f moves rearward while maintaining the engagement with theremoved-position holding surface 11 a 1 (i.e., while holding the secondlens group L2 on the eccentric optical axis Z1′) to bring theretractable zoom lens 10 into a fully retracted state as shown in FIGS.2 and 3B.

[0071] Obvious changes may be made in the specific embodiment of thepresent invention described herein, such modifications being within thespirit and scope of the invention claimed. It is indicated that allmatter contained herein is illustrative and does not limit the scope ofthe present invention.

[0072] The fundamental principle of the present invention is that anelement of a plurality of optical elements is removed from a position onthe optical axis of the plurality of optical elements to a differentposition outside of the optical axis, and the removed element and atleast one element of the remaining optical element(s) of the pluralityof optical elements are moved rearward along the optical axis, for thepurpose of refracting the plurality of optical elements from aready-to-photograph state which initially lie on a single optical axis.Accordingly, the structure of the retractable lens system according tothe present invention is not limited solely to that of the aboveillustrated embodiment as long as the structure is designed on thisfundamental principle.

[0073] For example, in a second embodiment, as shown in FIG. 11, whenthe retractable zoom lens 10 is in a fully retracted state, the firstlens group L1 can also be removed from the optical axis Z1 in additionto the second lens group L2, so that the first lens group L1 is radiallymoved to an eccentric optical axis (removable-element optical axis) Z1″and the second lens group L2 is radially moved to the eccentric opticalaxis Z1′. In the second embodiment, since all of the first through thirdlens groups L1, L2 and L3 are positioned so as to overlap in the samepositional range in the optical axis direction, the length (thethickness in the optical axis direction) of the retractable zoom lens 10at the fully retracted state is even further shortened.

[0074] Furthermore, the method of removing (radially moving) the lensgroups from the optical axis Z1 can also differ from that of the firstembodiment. For example, in a third embodiment shown in FIG. 13, theoptical axis Z1′ of the second lens group L2, which has been removedfrom the optical axis Z1, extends in a direction perpendicular to theoptical axis Z1. Alternatively, in a fourth embodiment shown in FIG. 14,the optical axis Z1′ of the second lens group L2, which has been removedfrom the optical axis Z1, extends in a direction inclined (not parallel)to the optical axis Z1. In other words, in the present invention, theoptical axis Z1′ of the optical element(s) removed from the optical axisZ1 can extend in a direction parallel to the optical axis Z1, as in thefirst embodiment (FIGS. 1 through 10), or can extend in a directioninclined to the optical axis Z1.

[0075] Furthermore, in the present invention, the radial direction ofmovement of the optical elements when being removed from the opticalaxis Z1 can be any desirable direction. For example, FIGS. 14 and 15show a rectangular camera body 40 having the retractable zoom lens 10 ofthe present invention. In FIG. 14, the second lens group L2 which hasthe smallest lens diameter is moved in directly upward direction. InFIG. 15, the second lens group L2 which has the smallest lens diameteris moved in an upper diagonal direction, and the first lens group L1which has the largest lens diameter is moved horizontally toward theleft side as viewed from the front. The present invention is not limitedto the examples shown in FIGS. 14 and 15 are examples, and thecombination (number) of the optical elements and the direction ofmovement when the optical element(s) is removed from the optical axis Z1is not limited thereto.

[0076] Although the second lens group L2 is the optical element amongthe optical elements of the photographing optical system which isremoved from a position on the optical axis thereof in the aboveillustrated embodiment of the retractable zoom lens, one or more of anyother optical element such as the diaphragm shutter S and the low-passfilter F can constitute the removable optical element(s) in the samemanner as the second lens group L2 of the above illustrated embodimentof the retractable lens system.

[0077] Although the above illustrated embodiment of the retractable lenssystem is a zoom lens, the present invention can also be applied to aretractable type fixed-focal-length lens.

What is claimed is:
 1. A retractable lens system having a plurality ofoptical elements; wherein all of said plurality of optical elements arepositioned on a common optical axis to constitute a photographingoptical system when said retractable lens system is in aready-to-photograph position; and wherein at least one removable elementof said plurality of optical elements is moved to a removed positionoutside of said common optical axis, and said removable element and atleast one element of the remaining elements of said plurality of opticalelements are moved rearward respectively, when said retractable lenssystem is in a retracted position.
 2. The retractable lens systemaccording to claim 1, wherein said removable element is positionedoutside of at least one element of the remaining elements of saidplurality of optical elements with respect to said common optical axiswhen said retractable lens system is in a retracted position.
 3. Theretractable lens system according to claim 1, wherein said removableelement moves rearward parallel to said common optical axis after beingmoved to said removed position when said retractable lens system movesto said retracted position.
 4. The retractable lens system according toclaim 1, wherein an optical axis of said removable element of saidoptical elements is parallel to said common optical axis when saidretractable lens is in said retracted position.
 5. The retractable lenssystem according to claim 1, wherein said optical elements include aplurality of said removable elements.
 6. The retractable lens systemaccording to claim 5, wherein each removable element of said pluralityof removable elements is moved in different directions from said commonoptical axis to each respective said removed position.
 7. Theretractable lens system according to claim 1, wherein a rotational axisof a rotational member for moving at least one of said plurality ofoptical elements along said common optical axis is eccentric to saidcommon optical axis of said photographing optical system.
 8. Theretractable lens system according to claim 7, wherein said removableelement of said optical elements is positioned within the periphery ofsaid rotational member when said retractable lens is in the retractedposition.
 9. The retractable lens system according to claim 7, whereinsaid rotational member comprises a cam ring.
 10. The retractable lenssystem according to claim 1, wherein said retractable lens isincorporated in a camera.
 11. The retractable lens system according toclaim 10, wherein said retractable lens system moves to said retractedposition when a main switch of said camera is turned OFF.
 12. A methodof retracting a retractable lens system having a plurality of opticalelements, wherein all of said plurality of optical elements arepositioned on an common optical axis to constitute a photographingoptical system when said retractable lens system is in aready-to-photograph position, said method comprising: moving at leastone element of said plurality of optical elements in a radial directionto a removed position outside of said common optical axis; retractingsaid removable element of said optical elements rearward after beingmoved to said removed position; and retracting at least one element ofthe remaining elements of said plurality of optical elements along saidcommon optical axis.
 13. The method of retracting a retractable lenssystem according to claim 12, wherein said removable element ispositioned outside of at least one element of the remaining elements ofsaid plurality of optical elements with respect to said common opticalaxis, when said retractable lens system is in a retracted position. 14.The method of retracting a retractable lens system according to claim12, wherein said removable element moves rearward parallel to saidcommon optical axis after being moved to said removed position.
 15. Themethod of retracting a retractable lens system according to claim 12,wherein an optical axis of said removable element of said opticalelements is parallel to said common optical axis when said retractablelens system is in said retracted position.
 16. A retractable zoom lenssystem having a plurality of lens groups, wherein at least a portion ofsaid lens groups are moved continuously along an optical axis to vary afocal length; wherein at least one radially movable lens group of saidplurality of lens groups is radially moved from among said plurality oflens groups so that said radially movable lens group and at least onelens group of the remaining lens groups of said plurality of lens groupsare positioned so as to overlap in the same positional range in saidoptical axis direction when said retractable zoom lens is in theretracted position.
 17. The retractable zoom lens system according toclaim 16, wherein said radially movable lens group is the smallest indiameter among said plurality of lens groups.
 18. The retractable zoomlens system according to claim 16, further comprising an adjustablediaphragm having an aperture, the diameter of which is variable; whereinsaid adjustable diaphragm is positioned between two adjacent lens groupsof said plurality of lens groups; and wherein said radially movable lensgroup is at a position behind said adjustable diaphragm when said zoomlens system is in use position.
 19. The retractable zoom lens systemaccording to claim 18, wherein said adjustable diaphragm serves as adiaphragm shutter.
 20. The retractable zoom lens system according toclaim 16, further comprising an adjustable diaphragm having an aperture,the diameter of which being variable; wherein said adjustable diaphragmis positioned between two adjacent lens groups of said plurality of lensgroups; and wherein said radially movable lens group is positionedclosest to said adjustable diaphragm among said plurality of lens groupswhen said zoom lens system is in ready-to-photograph position.
 21. Theretractable zoom lens system according to claim 20, wherein saidadjustable diaphragm serves as a diaphragm shutter.
 22. The retractablezoom lens system according to claim 16, wherein said radially movablelens group is at a position behind a frontmost lens of said plurality oflens groups.